This invention pertains to environmentally-friendly alternatives to organometallic antifoulants. These alternatives are efficacious at preventing biofouling by organisms, such as the zebra mussel (Dreissena polymorpha), and will minimize overall environmental impact.
Since their introduction into the Great Lakes in the late 1980's, zebra mussel infestations have spread via adjacent interconnected inland waterways and by trailering overland on boat hulls throughout large portions of the United States. Zebra mussels create an expensive biofouling problem by colonizing, and consequently clogging, freshwater intakes so severely that the antifouling costs to U.S. municipal and industrial power generating and water treatment plants is in the billions of dollars, with about 100-400 million dollars being spent annually in the Great Lakes basin alone.
Marine biofouling in general is even more costly, exceeding 5 billion dollars annually. Of major concern is colonization of seafaring vessel hulls by a variety of fouling organisms. This promotes corrosion and increases hydrodynamic drag, which increases fuel consumption and reduces maneuverability. Commercial chemical antifouling methods rely primarily on the use of paints or coatings embedded with copper, tin or zinc, or compounds containing these heavy metals, or combinations of these heavy metals and organic “booster” biocides. However, coatings have a limited life-time and require periodic re-application, which can be expensive and time consuming. Due to their persistence and the toxicity of their heavy metal components to other aquatic life, such antifouling strategies remain an environmental concern, and legal moratoriums restricting or banning the use of some of these strategies are in place and more are planned. Other antifouling methods include the combined drying and freezing of mussels, which has limited practical applications.
Blending zosteric acid, a known antifoulant isolated from eelgrass (Zostera marina) with a coating material has been used to produce an antifoulant coating. However, this antifoulant coating was short-lived and effective for less than 2 months due to hydrolysis of the active component (Walsh M A, 2003).
There have long been case reports by boaters claiming that marine biofouling is significantly reduced when hot sauce containing chili peppers is used as a paint additive (Perry, 1993). The characteristic “hot” sensation experienced when chili peppers are ingested orally is produced by the natural product component capsaicin (8-methyl-N-vanillyl-trans-6-nonenamide). In a controlled laboratory setting, capsaicin has proven to be an effective zebra mussel antifoulant (Cope et al., 1997). However, in initial antifouling field tests, capsaicin was not as effective as copper when simply mixed with paint applied to a surface or when applied to a surface as a dust. (Race and Kelly, 1996).
U.S. Pat. No. 5,629,045 pertains to an anti-fouling composition containing capsaicin in which the capsaicin is mixed with a corrosion resistant epoxy resin and a hardening catalyst and applied to the surface to be protected.
U.S. Pat. No. 5,629,045 pertains to coatings for the prevention of fouling by sea animals which include capsaicin incorporated into standard marine paints, impregnants, and varnishes.
U.S. Pat. No. 6,607,826 pertains to a plastic film applied to the outside of boat hulls or other structures to prevent fouling. Anti-fouling compounds such as capsaicin can be incorporated in the plastic film.
U.S. Patent Application Publication No. 2005/0080160 pertains to paints and coatings containing anti-colonization agents, including capsaicin.
International Patent Application Publication No. 2005/025314 pertains to capsaicin derivatives and their use as micro-organism repellents in paints and coatings.
International Patent Application Publication No. 2005/027642 pertains to repellent preparations containing capsaicin and a wax that can be used as a coating or an additive for paints or plastics.
There still exists a pressing need for new and effective antifouling technologies which are environment-friendly. This “green” technology will potentially result in billions of dollars of savings for both public and private institutions by preventing biofouling in an environmentally sound and responsible manner.